The present invention relates to sheet transport devices for use in copying machines, automatic document feeders or the like, and more particularly to a device which comprises a removable sheet guide member for guiding copy paper, document or like sheet for transport to a separating roller, or in which a sheet tray such as paper feed tray or discharge tray is removably provided.
Image forming apparatus such as copying machines or automatic document feeders for use in such image forming apparatus include a sheet transport device for feeding or discharging copy paper, documents or like sheets. The paper feed assembly of such a device generally comprises a document tray, paper feed roller, separating roller for preventing feed of more than one sheet, guide member for documents and the like (for example, as in the automatic document feeder disclosed in Unexamined Japanese Utility Model Publication SHO 60-167033).
FIG. 11 shows an example of paper feed assembly. With reference to this drawing, indicated at 101 is a main housing, at 102 a feed housing comprising a cover 102a and a bottom plate 102b. A pair of register rollers 103, a conveyor belt 104, etc. are arranged within the main housing 101. Disposed inside the feed housing 102 are a feed roller 105, separating roller 106, dispenser roller 107, etc. The feed roller 105 and the separating roller 106 are rotatably supported by unillustrated bearings on the feed housing 102. The feed roller 105 is driven in the direction of feed of documents, while the separating roller 106 is driven in the opposite direction, whereby double sheet feeding is prevented.
A document tray 108 is attached to the upstream-side end portion of the paper feed assembly. A document guide member 109 is provided between and adjacent to the document tray 108 and the conveyor belt 104. The document guide member 109 is so shaped as to cover the rotary shaft 106a of the separating roller 106 except the upper portion of the roller 106 and is fastened to the bottom plate 102b with screws for passing the document over the separating roller 106 toward the pair of register rollers 103.
The document tray 108 has its base portion attached to each side plate 102c extending upward from the bottom plate 102b with a pin 110 inserted from one side, whereby the tray 108 is made pivotally movable about the pin 110. Accordingly, documents can be placed on the tray 108 as unfolded to the solid-line position in FIG. 11, while when the tray 108 is in an upright position indicated in phantom lines in the drawing, the user can readily use a manual feed tray below the tray 108 or handle a paper cassette below the tray 108. The structure is usable, for example, for attaching a document delivery tray to the downstream-side end of the automatic document feeder or for attaching a copy paper manual feed tray or discharge tray to the body of the copying machine.
However, the conventional structure described has the following problems to be solved.
First with the above structure, the position of the separating roller 106 and the document guide member 109 relative to each other, especially the amount of projection of the roller 106 beyond the guide member 109 and the parallelism of these members become very important in enabling the separating roller 106 to effectively separate sheets of paper. Nevertheless, since the separating roller 106 and the guide member 109 are attached to the feed housing 102 individually independently of each other, the errors involved in the attachment directly influence the position of them relative to each other, making it difficult to position them accurately relative to each other. Especially because the guide member 109 is generally made of resin or like flexible member and is therefore prone to warping or distortion due to external conditions such as temperature, the two members can not always be held in a definite position relative to each other after assembling.
Further with the above structure, the document tray 108 needs to be attached to or removed from the automatic document feeder by inserting the pins 110 into the feeder or removing the pins therefrom at the front and rear sides of the feeder. Especially it is cumbersome to handle the pin 110 on the rear side of the feeder, for example, for maintenance. It is therefore desired to make the tray 108 attachable or removable more easily.
Since the automatic document feeder is made openable (pivotally movable) relative to the body of image forming apparatus, it is required that the feeder be attached to the body with good stability without the likelihood that the document tray will fall off when the feeder is opened or closed. Such an attachment problem is encountered, for example, with other sheet trays for use as attached to apparatus the body of which is openable, like the manual feed tray for copying machines of the clamshell type.